This invention relates to the art of orthodontic appliances and methods, and more particularly to a new and improved force adjusting mechanism and method of operating the same for use in orthodontic appliances.
Various orthodontic appliances have mechanisms or components which provide force for moving teeth and/or expanding the dental arches. During the course of treatment, as the teeth are moved toward the desired position/location, it is necessary periodically to adjust the mechanisms/components so that the required amount of force is continued to be applied to the teeth. Such force applying arrangements heretofore available have a number of limitations such as being cumbersome in design, being subject to failure caused by screw thread stripping or slipping and providing limited access to adjustment components due to intra-oral environment. All of these arrangements have the added disadvantage of requiring adjustment by a clinician thereby necessitating an office visit for each adjustment.
It would, therefore, be highly desirable to provide a force adjusting mechanism for orthodontic appliances which is effective and reliable in operation and which is easy to adjust by the patient or a parent or guardian without the need for an office visit to a clinician.
The invention provides a force adjusting mechanism for an orthodontic appliance wherein the appliance functions to move teeth and/or to expand the dental arch. The mechanism includes a shaft operatively coupled at opposite ends between a first portion of the appliance which is anchored in the patient's dental arch and a second portion of the appliance which applies force to one or more of the patient's teeth. A lock is slidable along the shaft to compress a spring between the lock and the second portion of the appliance. Cooperating structures on the shaft and on the lock provide a unidirectional ratchet movement of the lock along the shaft. Thus, the lock may be advanced one step at a time in one direction only, preferably manually using an implement for engaging the lock, to compress the spring to apply force to one or more of the patient's teeth. Advantageously, this may be done by the patient or a parent or guardian without the need for an office visit to a clinician. The cooperating structures can include a series of successive detent formations along the shaft and a component on the lock moveable into and out of the detent formations thereby avoiding thread stripping or slippage.
The foregoing and additional advantages and characterizing features of the invention will become clearly apparent upon a reading of the ensuing detailed description together with the included drawing.